Thixotropic lubricant grease and thickener therefor



3,144/il Patented Aug. 11, 1964 3,144,410 THIXOTROPIC LUBRICANT GREASEAND THICKENER THEREFOR Thornton P. Traise, Chicago Heights, Ill.,assignor to Standard Oil Company, Chicago, 111., a corporation ofIndiana No Drawing. Original application Dec. 23, 1960, Ser. No. 77,856.Divided and this application Oct. 9, 1962, Ser. No. 238,818

5 Claims. (Cl. 252-51.5)

This invention relates to novel amides and to their use as thickeningagents to make thixotropic greases.

This is a division of application Serial No. 77,856, filed December 23,1960.

In the operation of machinery for intermittent service, it is frequentlydesirable to have a lubricant which will posssess the consistency of agrease and thus remain in place during periods of non-use, but whichwill have the fluidity and lubricity of a liquid oil when the equipmentis in operation. Lubricants of this type, termed thixotropic greases,are well known. Few, however, are able to combine effective thixotropywith other desiderata of greases, such as temperature and mechanicalstability.

A primary object of the invention is to provide an improved thixotropicgrease capable of lubricating over broad ranges of temperature. Anotherobject is to produce a thixotropic grease which is an attractive, brightand smooth gel. A further object is to provide a thixotropic materialwhich rapidly reverts to its original grease consistency after repeatedperiods of mechanical working. Yet an additional object is to producenovel amide compounds. Other and more particular objects Will becomeapparent as the description herein proceeds in detail.

According to the invention, it has been discovered that superiorthixotropic greases are obtained when a normally liquid lubricantvehicle is thickened to grease consistency with one or more hydroabietyloxamide compounds having the general formula tr t where R and R are thesame or different hydroabietyl radicals selected from the groupconsisting of a dehydroabietyl radical, a dihydroabietyl radical, andtetrahydroabietyl radical. The radicals R and R can contain substituentssuch as, for example, alkyl, alkoxy, cyano, aryl, hydroxy, carboxy,halogen, nitro and other substituent group.

The general structural formula of the hydroabietyl radicals are:

The inventive compounds can be prepared, for example, by heating amixture of a hydroabietyl amine and an oxalic acid diester in theequivalent weight ratio of 1:1, at a temperature within the range ofroom temperature (about 20 C.) to about 220 C. in the presence of abasic catalyst. Strong bases, i.e., those which ionize completely inwater such as NaOH, or their precursors such as metallic Na or otheralkali metals, appear to olfer the most rapid reaction rates,particularly when finely divided. Any diester may be used, e.g., thoseof alkanols having 1-5 carbon atoms each, such as methyl, ethyl, propyl,i-butyl, t-butyl, etc. The alkanol by-product may be volatilized offduring reaction.

Examples of hydroabietyl amines, i.e., aliphatic amines attached to analicyclic structure, which can be used in the preparation of the abovedescribed ureido compounds are dehydroabietyl amine, dihydroabietylamine and the tetrahydroabietyl amine or mixtures of such amines. Aparticularly well suited amine is a product marketed by Hercules PowderCompany as Rosin Amine D. The product is prepared by the catalytichydrogenation of Rosin Nitrile D prepared by the action at elevatedtemperatures of ammonia on hydrogenated rosin. Distilled and undistilledgrades are available as Amine 750 and Amine 751. The Rosin Amine D is amixture of hydroabietyl amines in the following approximate proportion:

Rosin Amine D, percent The following is illustrative of the apparentreaction which takes place in the preparation of the inventivethickener.

Dehydroabietylamiue Oxalic acid diester H O O H The compounds abovedefined and described have been found to be exceptionally eflective asoil-thickeners to obtain lubricating grease compositions which exhibitgood thixotropic properties, high thermal stability, and high droppoints. Such grease compositions are obtained by incorporating in asuitable normally liquid oleaginous lubricant vehicle from about 2% toabout 25% by weight, of at least one compound having the above. Thegrease can be prepared by placing the desired amount of the diester ofoxalic acid and hydroabietylamine in a high temperature grease kettle,or other suitable heating equipment. To the mixture is added less than apercent or so of sodium metal catalyst, and the mixture heated to atemperature of about 20 to 220 C. (advantageously at least high enoughto boil off the alkanol), and maintained at said temperature for 0.1-10hours. The lubricant vehicle may then be added, or else the mixture mayfirst be cooled and washed with alcohol or ether and then reheated. Thethickener and vehicle form a homogeneous gel at about 105-110 C.; otheradditives may be added at this stage. The grease product is thencooledeither slowly without agitation or by shock coolingand mayoptionally be finished by cooling and milling. The preparation ofgreases of the herein described invention lends itself very favorably toeither batch or continuous manufacture methods.

Oleaginous lubricant vehicles which can be thickened with the hereindescribed compounds to form greases of the present invention can bemineral lubricating oils, silicone polymer oils, synthetic hydrocarbonlubricating oils, synthetic lubricating oils such as polyalkyleneglycols and their derivatives, high molecular weight esters ofdicarboxylic acids, polyfluoro derivatives of organic compounds such asthe trifluorovinyl chloride polymers known as fiuorolube (made by HookerChemical Company) and the trifluorochloroethylene polymers, known asKel- F-40 (made by The M. W. Kellogg Company), and other lubricantvehicles.

Other oleaginous vehicles which may be employed herewith are, forexample, mineral oils in the lubricating oil viscosity range, e.g., fromabout 50 S.S.U. at 100 F. to about 300 S.S.U. at 210 F. These mineraloils may be suitably solvent extracted, with phenol, furfural, B,B'-dichlorodiethylether (Chlorex), liquid S nitrobenzene, etc. Syntheticlubricating oils resulting from polymerization of unsaturatedhydrocarbons or other oleaginous materials within the lubricating oilviscosity range such as high molecular weight polyoxyalkylene compoundssuch as polyalkylene glycols and esters thereof, aliphatic diesters ofdicarboxylic acids such as the butyl, hexyl, 2- ethylhexyl, decyl,lauryl, etc. esters of sebacic acid, adipic acid, azeleic acid, etc.,may be thickened by the compounds of the present invention to produceexcellent greases. Polyfluoro derivatives of organic compounds,particularly hydrocarbons, in the lubricating oil viscosity range, andother synthetic oils, such as esters of aliphatic carboxylic acids andpolyhydric alcohol, e.g. trimethylolpropane pelargonate, pentaerythritolhexanoate, can be used as suitable oil vehicles.

The following examples illustrate the preparation, use in greases, andtesting of the inventive compounds.

Example 1 Two moles of Rosin Amine D and one mole of diethyl oxalatewere charged to a glass flask and a small amount of sodium metal addedto catalyze the reaction. The mixture was heated over a period of 5-6hours to 165 C., during which time the ethanol by-product was removed asa vapor. The crude reaction product melted at 104-105 C. It waspredominately dehydroabietyloxamide.

Example II A mineral oil base grease was prepared by heating 14 parts ofthe above reaction mixture with 86 parts by weight of a solventextracted SAE 40 base oil to 120 C. Upon slowly cooling the grease toroom temperature without agitation, a grease having an unworked ASTMpenetration of 215-220 was prepared. It had a drop point of 169 F. Evenafter standing at room temperature for several months, no leakage wasobserved.

Example 111 A grease was prepared according to the procedure of ExampleII, except that the heated thickener-oil mixture was shock chilled tobelow room temperature in a few seconds on a conventional chilling roll.The resultant grease had an unworked AST M penetration of 203 and a droppoint of 172F.

Wheel bearing test.This test measures the ability of bearing grease toresist leakage. The grease is applied to 4 a modified front wheel huband spindle. The hub is rotated at 660:30 r.p.m. for 6 hours. Leakage ofoil is measured by weighing the parts and the condition of the bearingsis recorded. This test is run at ambient temperatures.

The measured internal temperature was ISO- F. There was no leakage orslumping of either grease in the hub or spindle, and the bearingsremained well lubricated. Even after 12 hours there was no slumping orleakage.

Rate of rec0very.Samples of thixotropic greases are worked until theybecome fluid; then, as the grease recovers its consistency, penetrationmeasurements are made.

PE NETBATION Mehanical stability.-The grease of Example III is Worked inan ASTM grease worker, then allowed to stand for 24 hours beforepenetration measurements are made.

No. of strokes: Penetration 5,000 214 10,000 250 20,000 266 50,000 310These data show that both greases are outstanding, with theshock-chilled grease of Example HI giving a somewhat better yield,recovers its consistency faster, and has a slightly higher drop-pointthan the slow-cooled samples. The wheel-bearing test showed that bothgreases are excellent for lubricating and sealing anti-frictionbearings.

Acceptable thixotropic properties are apparently confined to thespecific types of greases described herein. Octadecyloxamide was foundto be an ineflicient thickener for lubricating grease; this grease wasthixotropic but very slowly reversible. Attempts to make a highermelting thickener by reacting ethyl oxalate with aromatic amines such asp-chloroaniline or toluidine were unsuccessful, as the thickener couldnot be satisfactorily dispersed in the oil. Dehydroabietylmalonamide,dehydroabietylsuccinamide, and dehydroabietyladipamide were not able tothicken oil.

The grease product of the present invention can contain one or more wellknown additives or addition agents to impart various desired propertiesthereto such as, by way of example, antioxidants, extreme pressureagents, corrosion inhibitors, anti-leak agents, anti-foam agents,mineral lubricants such as graphite, molybdenum sulfide, etc.

I claim:

1. A thixotropic lubricating grease comprising a normally liquidlubricant vehicle thickened to grease consistency with at least onecompound having the general formula HOOH wherein R and R arehydroabietyl radicals selected from the group consisting of adehydroabietyl radical, a dihydroabietyl radical, and atetrahydroabietyl radical.

2. A thixotropic lubricating grease as described in claim 1 wherein saidnormally liquid lubricant vehicle is a hydrocarbon lubricating oil.

3. The method of preparing a thixotropic lubricating grease comprising anormally liquid lubricant vehicle thickened to grease consistency with acompound having the general formula O O RN i' lNR' in which R and R arehydroabietyl radicals selected from the group consisting of adehydroabietyl radical, a di hydroabietyl radical, and atetrahydroabietyl radical, comprising mixing an oxalic acid diester anda hydroabietyl amine, in the equivalent weight ratio of 1:1, heatingsaid mixture to a temperature of from 20 to about 220 C., maintaing saidtemperature for a time suflicient for by-product alkanol to be removed,commingling the resultant product with a normally liquid lubricantvehicle,

heating the resultant mixture to a temperature sufficient to obtain ahomogeneous solution, and cooling the resultant grease.

4. The method of claim 3 wherein said cooling is effected slowly withoutagitation of said mixture.

5. The method of claim 3 wherein said cooling is affected by shockchilling.

Swakon et al June 14, 1955 Traise et al Sept. 4, 1962 UNITED, STATESPATENT OFFICE,

CERTIFICATE OF CORRECTION Patent No 3, 144,410 August 11 1964 ThorntonP. Traise It is hereby certified. that error appears in the abovenumbered patent requiring. correction and that the said Letters Patentshould read as corrected below.

Column 2, lines 47 to 57, the upper center portion of the formulareading:

Signed and sealed this 5th day of January 1965,

O H H O O H I II (SEAL) Attest:

EDWARD J. BRENNER; Commissioner of Patents ERNEST W. SWIDER' AttestingOfficer

1. A THIXOTROPIC LUBRICATING GREASE COMPRISING A NORMALLY LIQUIDLUBRICANT VEHICLE THICKENED TO GREASE CONSISTENCY WITH AT LEAST ONECOMPOUND HAVING THE GENERAL FORMULA